Bina-Stein M, Crothers D M
Biochemistry. 1975 Sep 23;14(19):4185-91. doi: 10.1021/bi00690a006.
We have compared the molecular mechanism of thermal unfolding for native tRNA fMet (Escherichia coli) and the denatured species produced by annealing at pH 4.3. Relaxation kinetic measurements reveal that the transitions assigned to melting of TphiC, anticodon, and acceptor stem helices at neutral pH remain essentially unaltered at pH 4.3, but the transition corresponding to coupled melting of tertiary structure and dihydrouridine helix is greatly affected. The Tm of this region is more than 20 degrees higher at pH 4.3 and it has a larger enthalpy formation than in the native state. The transition dynamics are also considerably changed. In contrast to the native structure, tRNA fMet1 and tRNA fMet3 have similar tertiary structure stabilities at pH 4.3. We conclude that the structural difference between native and acid-denatured forms is localized in the tertiary structure-dihydrouridine helix cooperative interaction region of the molecule.
我们比较了天然甲硫氨酸转运核糖核酸（大肠杆菌）热解折叠的分子机制以及在pH 4.3退火产生的变性物种。弛豫动力学测量表明，在中性pH下归属于TphiC、反密码子和受体茎螺旋解链的转变在pH 4.3时基本保持不变，但对应于三级结构和二氢尿嘧啶螺旋耦合解链的转变受到很大影响。该区域的熔解温度在pH 4.3时比天然状态高20多度，并且其焓形成比天然状态更大。转变动力学也有相当大的变化。与天然结构不同，甲硫氨酸转运核糖核酸1和甲硫氨酸转运核糖核酸3在pH 4.3时具有相似的三级结构稳定性。我们得出结论，天然形式和酸变性形式之间的结构差异位于分子的三级结构 - 二氢尿嘧啶螺旋协同相互作用区域。
